1. Field of the Invention
The invention relates to an X-ray examination apparatus, including an X-ray image intensifier tube provided with an entrance screen with a photocathode, an electron-optical imaging system, and an exit section with an exit window, an exit phosphor screen, and a light-optical image transfer system.
2. Description of the Related Art
An X-ray examination apparatus of this kind is known from U.S. Pat. No. 4,809,309.
In a system described therein, the image transfer in the exit section often gives rise to the loss of a comparatively large part of the luminescent light to be generated in an exit screen. As a result, the brightness of an image-carrying light beam at the area of a subsequent image recording system, for example a television pick-up tube, a CCD camera, a film foil etc. is usually too low for optimum imaging. This situation can usually be improved only by way of an undesirable increase of the radiation dose in the imaging X-ray beam.
Various means have been proposed for improvement, but the gain in respect of light yield is then at the expense of a loss in respect of another property of the image transfer between the incident photoelectron beam and the recording system, for example resolution, optical imaging etc.